This application claims the priority of Korean Patent Application No. 2002-594 filed on Jan. 5, 2002 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to an optical disk drive, and more particularly, to a cover plate for an optical disk drive designed to reduce vibration and noise occurring during the rotation of a disk.
2. Description of the Related Art
An optical disk drive is an apparatus that reads data from and writes data onto a recording medium such as a compact disk (CD) or a digital video disk (DVD) by emitting a laser beam onto the disk. An important research area in this respect is the possibility of achieving high speed and reducing noise and vibration of optical disk drives.
FIG. 1 is a schematic exploded perspective view of a conventional optical disk drive, and FIG. 2 is a vertical cross-section showing an assembled state of the optical disk drive of FIG. 1.
Referring to FIGS. 1 and 2, the conventional optical disk drive includes a main frame 10, a deck assembly 20 installed into the main frame 10, a tray 30, which has a surface 31 on which a disk D is to be placed, for loading/unloading the disk D by horizontally sliding into or out of the main frame 10, and a cover plate 40 installed above the main frame 10 for covering the disk D and the deck assembly 20.
The deck assembly 20 consists of a turntable 23 that accommodates the disk D transported by the tray 30, a spindle motor 24 for rotating the turntable 23, a deck plate 21 on which an optical pickup 25 for recording and playing back information on the disk D is mounted, and a deck base 22 that supports the deck plate 21 and is installed so that it can rotate with respect to the main frame 10 by means of a hinge pin 22a projecting out on its sides.
Reference numeral 11 denotes a loading motor for driving the tray 30 so that it can move into or out of the main frame 10. Reference 12 denotes a cam having a cam hole (not shown) into which a cam protrusion 22b of the deck base 22 is fitted. When driven by the loading motor 11, the cam 12 turns to move the cam protrusion 22b up or down. Thus, as the cam 12 turns, the cam protrusion 22b moves up and down along the cam hole, which enables the deck assembly 20 to rotate about the hinge pin 22a. In this configuration, when the disk is put in the tray 30 and introduced into the main frame 10, the cam 12 turns to rotate the deck assembly 20 so that the disk D is loaded on the turntable 23. Thereafter, when driven by the spindle motor 24, the turntable 23 rotates to enable the optical pickup 25 to play back information written on the disk D or record new information on the disk D.
A disk clamp 51 is combined into the cover plate 40 for clamping the disk D placed on the turntable 23. For this purpose, the cover plate 40 has a through hole structure 42 through which the disk clamp 51 is coupled to the disk D. A circular step 43 is formed around the inner circumference of the through hole structure 42 so that the outside edge of the disk clamp 51 is caught on the circular step 43. Furthermore, magnetic substances 51a and 23a are disposed in a bottom portion of the disk clamp 51 and in a top portion of the turntable 23, respectively. The disk D put on the turntable 23 is clamped between the turntable 23 and the disk clamp 51 due to an attractive force between the two magnetic substances 51a and 23a. 
Reference numeral 52 denotes a cap attached to the cover plate 40 by a predetermined attaching means for preventing separation of the disk clamp 51 from the through hole structure 42. Reference numeral 41 denotes a groove for enhancing the strength of the cover plate 40 made of thin metal.
In an optical disk drive constructed in this way, high-speed rotating disks will usually undergo vibration. The vibration of a disk is known to be mainly-caused by excitation due to mass unbalance and spindle motor bearing defects, mechanical resonance, excitation due to instability in a rotating disk at critical speed, and disk fluttering. The vibration of a disk during the operation of an optical disk drive will degrade the reliability in recording/playing back data. Thus, in order to secure the reliability of an optical disk drive, there is a need to damp out vibration of the disk induced during its operation. However, the conventional optical disk drive described above has not yet adopted a structure to reduce vibrational effects of the disk.
Furthermore, as the speed of optical disk drives increases, a disk placed therein rotates with high-speed, thereby generating additional noise. Some examples include noise due to friction between the surface of a rotating disk and surrounding air, noise due to air flow created by a pressure difference between the inner and outer circumferences of the disk, noise generated as a result of the air flow colliding with walls around the surface of a tray on which the disk is to be placed, and noise due to turbulence created around the rotating disk. Since optical disk drives are adopted mostly in personal computers requiring its use in very quiet circumstances, the noise becomes a big problem that decreases work efficiency.
Conventionally, a passive method is used to mitigate noise; that is, gaps in doors, bezels, or main frames are closed with a sound-absorbent material or sound-insulating material to prevent noise from escaping. Recently, another method has proposed installing a separate noise controller in an optical disk drive.
FIG. 3 shows a disk chucking device used in an optical disk drive, the application of which was filed on May 29, 1999, by an applicant of this invention under Korean Patent Application No. 10-1999-019598 and laid open on Dec. 15, 2000, under Korean Patent Application Laid-open No. 2000-075152. In the optical disk drive shown in FIG. 3, a chuck plate 80 is provided between a disk D and a cover plate (not shown) to reduce various kinds of noise due to the rotation of the disk D. The chuck plate 80 is approximately disk-shaped and has a pair of holding portions 84 attached to the main frame 60 on both sides thereof. The chuck plate 80 further has a chuck 82 in the center. The chuck 82 is rotatably installed to perform chucking on the disk D placed on the turntable 62. A groove 86 is formed in the bottom edge of the chuck plate 80 for reducing various kinds of noise resulting from rotation of the disk D. Since noise being discharged outside has a drastically low acoustic energy density due to the presence of the groove 86, this allows noise reduction similar to a muffler of a car. Reference numerals 64, 66, and 70 denote a deck assembly, an optical pickup and a tray, respectively.
The conventional methods for reducing noise described above involve attaching a separate noise-insulating or noise-absorbent material to the gap in the optical disk drive or manufacturing a separate device such as a chuck plate to be installed between a disk and a cover plate. The methods require cumbersome and costly work thereby reducing productivity.